--15-- 
The restriction pattern in Fig. 2 specifies that the sen-- 
tence to be generated should contain a transitive verb 
which belongs to either semantic class C1 or C2. The verb 
should govern (I) a noun as the subject of the sentence, 
(2) an object which is to be selected from the words in 
semantic class C15 or the specified words W 1 and W2, and 
(3) an adverb which does not belong to semantic class C19. 
The subject of the sentence should not govern an adjective. 
As illustrated in the pattern, each node in a pattern 
contains a word class and selection restrictions which are 
positively or negatively specified in terms of semantic 
class(es), specific word(s) or a word class. Restriction 
patterns are stored in the following form: Q-PIP2..oPn. 
Q is a single pattern, or a combination of patterns, and 
PIP2...P n are single restriction patterns. Essentially, 
Q-PIP2...Pn is e rule which specifies that if a sentence 
(or string of sentences) whose sentence skeleton(s) matches 
Q, then it can be followed by a sentence whose sentence 
skeleton is one of these Ps. Thus, one of these Ps is 
randomly selected to be used as a restriction pattern for 
a succeeding sentence. The pattern selection procedure is 
not yet coded. At present, strings of restriction patterns 
are given directly to the pattern selection routine. The 
generation program generates strings of sentences under 
the control oz direction of the restrictions specified in 
the patterns. The use of restriction patterns to control